Lifting carriages of this type are equipped with a tiltably mounted carrier transom having adjustable transom sections adaptable to the lengths of different warp beams. Each adjustable transom section is equipped with a carrier arm which in turn holds at its free end a gripper for the shaft of a warp beam, which may be a hollow shaft.
The carrier transom in conventional warp beam lifting carriages is hydraulically operated and the carrier arms are in turn equipped with a fine level adjustment mechanism in order to assure the exchange of an empty warp beam by a full warp beam without any troubles. For this purpose, it is necessary that the floating axle stubs extending axially out of the warp beam shaft are axially precisely aligned with the respective floating bearings in the loom. More specifically, it is especially necessary to precisely align the carrier arm axis of the lifting carriage with the axis of the warp beam shaft prior to the insertion of the floating axle stubs. The alignment of the carrier arms of the lifting carriage, more specifically, the alignment of the warp beam axis with the axis of the floating bearings for the stubs in the loom must be precise in the vertical direction relative to the elevation of the bearing axis and horizontally relative to the insertion depth of the carriage into the loom so that the warp beam axis coincides or rather is axially aligned with the axis of the two floating bearings. Only when this alignment is precisely assured, is it possible to insert the floating axle stubs supported in the floating axle bearings in the loom, into the respective sockets at the ends of the warp beam shaft.
Since a full warp beam has a substantial weight, the carriage holding such a full beam is also heavy, and a precision adjustment of the carriage by manual means, is difficult and accordingly time consuming.
Further, after the warp beam has been inserted into the loom, it is necessary to also align the beam laterally relative to the loom in order to assure a parallel and rectangular thread withdrawal from the warp beam and a respective warp thread supply to the heald shafts. This additional lateral adjustment is also time consuming and hence adversely affects the productivity of the loom.
Even for removing an empty warp beam out of the loom, the carrier arms of the lifting carriage must also be exactly aligned with regard to elevation and insertion depth relative to the warp beam shaft. If the alignment is less than precise, it becomes impossible to withdraw the floating axle stubs which become jammed in the bearings due to the friction between the floating axle stubs and the respective bearings. As a result, any deviations from a full alignment of the axle stubs with the central longitudinal rotational axis of the warp beam, must be kept within a permissible very small deviation range.